O impacto das modificações pós-ocupação no desempenho térmico de HIS: estudo de caso em Uberlândia-MG

Since 2009, more than four million social housing units (HIS) have been delivered in Brazil. Despite the positive impact on the housing deficit, HIS are often criticized for their design and construction quality. Residents report problems like thermal discomfort, high maintenance costs, lack of security, and the need of more built-up area. Once dissatisfied, the users modify the buildings in order to meet their demands. When modified, the buildings will be susceptible to problems, such as natural ventilation reductions and changes on heat fluxes through surfaces, and thus, they will be susceptible to possible changes in thermal performance and increases in energy consumption. Aiming to measure the impacts of modifications performed by the dwellers, modifications in single-family HIS, at a neighborhood called Residencial Pequis in Uberlândia-MG, were studied in this work. 18 cases were considered, combining the addition of walls, garages and bedrooms, with external walls in three colors. The impacts were measured by the building’s thermal performance, calculated with the simulation method from the ABNT NBR 15575-1:2021, and by the cost of energy consumption for air conditioning. The results showed that, in general, the buildings had their thermal performance improved with the addition of bedrooms. However, despite the changes in the geometry, the colors of the external walls caused the biggest impacts on thermal performance and energy consumption. For the building with the addition of walls around the lot, garage and a bedroom, for example, there was Minimum thermal performance with green external walls, Intermediate thermal performance for sand-colored external walls, and Superior thermal performance for white external walls. The analysis of the results also showed that, in some cases, despite resulting in lower thermal loads, the use of lighter colors led to non-compliance with the minimum operating temperature requirements of NBR 15575-1. In general, changes in geometry and the use of darker colors cause an increase in thermal loads and consumption for conditioning. This increase, among buildings with the same geometry, reaches 46% when comparing the building with the addition of walls around the lot, a bedroom and a garage, with external walls in white and green colors. Therefore, it was concluded that the demands of HIS users must be correctly considered in the design phases of these buildings. Modifications and expansions that do not follow the projects premises, result in problems such as a reduction in the level of thermal performance and an increase in energy consumption, which, in the current national scenario, with an energy crisis and a large rate of default on electricity bills, is even worse. By consulting the PostOccupation Analyzes performed locally and using computer simulations, designers and project managers can have a better understanding of the residents demands and, therefore, avoid the possible consequences of unanticipated changes.